1. Field of the Invention
The present invention pertains to an apparatus for transporting a hub, including, for example, a mechanism for transporting a pelletizer knife hub.
2. Description of the Related Art
Many containers and other items are manufactured from plastics. Examples include motor oil containers, fruit juice containers, trash bags, tool covers, and many other items too numerous to list. These items are often manufactured through a molding, extrusion, or blowing process. The raw material typically used in the manufacturing process is provided in the form of pellets manufactured from a polymer, such as polyethylene.
Certain processes for manufacturing the pellets themselves involve the use of a pelletizer system. In many such systems, a melted plastic resin is forced through an extruder at high temperatures and pressures. The resin is forced through a die plate having up to 600 extrusion holes, with the resin being forced at pressures in excess of 600 psi. The extruded resin passes through the extrusion holes into an underwater chamber. The resin is then cut into small pieces by a series of knives which are rotated within the underwater chamber against the face of the die plate. As the resin is cut, it is cooled by circulated water, causing hardening of the material into numerous individual pellets. The pellets are then carried from the chamber downstream by the circulated water for drying and transport to customers.
FIG. 1 and FIG. 2 depict a known knife hub which is rotated within a pelletizer system. FIG. 1 presents a side view of a knife hub 50 as sold under the mark KOBE(trademark). The knife hub 50 carries a plurality of knives 52 around its outer circumference. Each knife 52 has a blade surface 53 which rides closely along the die plate (not shown) in order to cut the resin. The blades are secured to the hub 50 by bolts 55 secured through the hub 50. Typically, 16 to 24 knives 52 are radially disposed about the outer circumference of the hub 50.
The hub 50 is rotated about a shaft 56. The shaft 56 typically comprises an outer polygonal surface 54 which mates to a rotary motor shaft (not shown). The shaft 56 is more fully seen in the perspective view of the hub 50 in FIG. 2.
The hub 50 also comprises a collar 58. The collar 58 is offset from a body 57 of the hub 50, leaving a gap between the collar 58 and the hub body 57. The portion of shaft 56 residing within the gap is shown in FIG. 2 at 56xe2x80x2. Shaft 56xe2x80x2 is generally circular in cross-section in order to receive a clamp (shown in FIG. 3) for aid in transporting.
It is periodically necessary to remove the knife hub 50 in order to inspect, repair, or replace the knives 52. A pelletizer knife hub transport mechanism 10 is used to maneuver a pelletizer knife hub 50 into and out of service with a plastic resin pelletizer system.
FIG. 3 presents a perspective view of a known transport mechanism 10 as is used for transporting a pelletizer knife hub, such as hub 50 shown in FIG. 2. The known transport mechanism 10 provides an elongated rail 15. At one end of the rail 15 is a clamp 30. The clamp 30 includes opposite clamping members 32, 34 which are selectively opened and closed. T-bolt 38 aids in securing and releasing the opposite clamp members 32, 34 in order to open and close the clamp 30.
The clamp 30 is configured to engage the shaft 56xe2x80x2 of the pelletizer knife hub 50, such as the hub 50 shown in FIGS. 1-2. To aid in transport, a hoisting system is needed. To this end, the known transport mechanism 10 provides a hoisting connector 24. The hoisting connector 24 defines a durable member fastened to the elongated rail 15 between the opposite ends. The hoisting connector 24 typically includes an eyelet 26 or other opening configured for receiving a hook 300. The hook 300 is connected to a hoisting system (not shown) such as a bridge crane, an arm crane, or even a stationary block and tackle for providing a mechanical advantage in maneuvering the transport mechanism 10. One or more cables 310 connect the hoisting hook 300 to the hoisting system.
To further aid in the transport of a pelletizer knife hub 50, a counter-weight 20 is provided. The counter-weight 20 is normally positioned proximate to the hoisting connector 24 when the transport mechanism 10 is not carrying a hub 50. However, the counter-weight 20 is slidable along the elongated rail 15 to the end opposite the clamp 30 when the clamp 30 engages the shaft 56xe2x80x2 of the hub 50. In this way, the transport mechanism 10 is balanced.
A counter-weight connector 22 is provided in order to connect the counter-weight 20 to the elongated rail 15. The connector 22 is slidable along the elongated rail 15 in order to permit adjustment of the longitudinal position of the counter-weight 20. However, known counter-weight connectors 22 do not swivel relative to the elongated rail 15. Likewise, the hoisting system connector 24 does not swivel about the longitudinal rail 15.
Disadvantages have been encountered with use of the known transport mechanisms 10. First, it is necessary during the removal and maneuvering of a knife hub 50 to rotate the knife hub 50 from its operational vertical position to a horizontal position. In this respect, knife hubs are serviced and maintenanced while they are on a work stand in the horizontal position. This typically requires that the knife hub be placed manually onto the ground in the horizontal position for subsequent transport to a maintenance area. However, as noted, the known transport mechanisms 10 have no swiveling parts, making rotation of the knife hub 50 into a horizontal position difficult.
Those of ordinary skill in the art will further appreciate that the manipulation of a knife hub 50 is extremely difficult. In this respect, the knife hub typically weighs in excess of 100 pounds and cannot easily be manipulated by a single individual, even when supported by a transport mechanism 10. Use of the currently known transport mechanisms 10 necessarily requires at least some manual manipulation of the hub 50.
Other disadvantages have been encountered in connection with known transport mechanisms 10. For example, once a hub 50 has been removed from a pelletizer system and lowered to the ground, the clamp 30 must be removed. A crew removing a hub 50 will place the hub 50 on the ground in a horizontal position, with the clamp 30 on top of the hub 50. The hub 50 is then typically rotated manually 180 degrees in order to set the hub 50 within a transportation box or to perform maintenance on the hub. Additional manual manipulation is required during maintenance, including subsequent manual rotation of the hub 50 in order to reattach the hub to the clamp 30 after knives 52 are installed.
Examples of patents generally pertaining to apparatus that provide leverage for handling a device include U.S. Pat. Nos. 2,925,300; 4,759,674; and 5,088,610; French Patent Nos. 1,498,313; and 2,403,281. In particular U.S. Pat. Nos. 2,925, 300, 5,088,610; and FR 1,498,313 disclose a material handling device which is transported through an overhead conveyance system. However, a device including a clamp which will suitably engage a pelletizer knife hub in a sufficiently secure fashion to enable transport and manipulation of the hub is not suggested.
Thus, there is a need for an improved transport mechanism for a pelletizer knife hub. A need further exists for a pelletizer knife hub transport mechanism capable of rotating and otherwise manipulating a clamp while engaging the hub. Further, a need exists for a knife hub transport mechanism that swivels relative to the hoisting system.
Mechanisms and methods for transporting a hub are provided. For example, transport mechanisms for a pelletizer knife hub are disclosed. The mechanism first comprises a clamp for selectively engaging and releasing the shaft of the pelletizer knife hub. The clamp is connected to a support bar. The support bar, in turn, has a hoisting connector for being raised, lowered, and maneuvered by a hoisting system.
In certain embodiments of the present invention, the clamp is rotatable relative to the hoisting connector. In one embodiment, a counter-balance to the hub is provided. In another arrangement, the hoisting system supports the hub normally above the hub for balancing the system.